<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <style>
    .box {
      width: 300px;
      height: 300px;
      box-sizing: border-box;
      border: 1px solid black;
      display: flex;
      flex-direction: column;
    }
  </style>
  <body>
    <div class="box">
      <div class="header"></div>
      <div class="content">
        <div class="left"></div>
        <div class="center"></div>
        <div class="right"></div>
      </div>
      <div class="footer"></div>
    </div>
  </body>
</html>
